A genome-wide search for wild-species alleles that increase horticultural yield of processing tomatoes.

To identify QTLs associated with horticultural yield it is necessary to conduct replicated plot trials of the tested genotypes. The first step in the utilization of an introgression-line (IL) population of Lycopersicon pennellii in a processing-tomato variety (M82) for mapping such QTLs was to screen 51 ILs in a non-replicated plot trial. The results of this survey were compared to those obtained in a replicated trial of the same genotypes grown as single plants at wide spacing. Fruit characteristics were similar between the two stands, but yield was generally different. Eight lines that outperformed the control in the plot survey were subjected to detailed analysis in the following year. The effects of these introgressions, measured on single plants, were reproducible relative to the previous year's results. In a replicated plot trial of these ILs and their hybrids involving two genetic backgrounds, the product of yield and total soluble solids (horticultural yield) in seven of the eight hybrids was 7-13% higher than that of their nearly isogenic controls. The results revealed a consistent trend in the interaction between introgression effects and genetic background. Combining the two introgressions with the largest contribution to horticultural yield in plots resulted in a 20% increase relative to the control in the third year. This research highlights the potential of wild germ plasm for yield improvement and the ability of nearly isogenic populations to achieve this goal.